System.ServiceModel.FaultException - The process cannot access the file 'xxx' because it is being used by another process - wcf

Question

I have a webservice WCF which log requests at the end of the process :
public void xxxxx(string sXmlIn, out string sXmlOut)
{
[...]
// log
log.PrintDatas = bPrintDatas;
log.sXmlIn = sXmlIn;
log.sXmlOut = sXmlOut;
log.error = error;
log.toFile();
}
Here is my Log class :
public class LogFile
{
public String sXmlIn;
public String sXmlOut;
public Error error;
private bool bPrintDatas;
public bool PrintDatas
{
set { bPrintDatas = value; }
}
private bool bInitWs;
public bool InitWs
{
get { return bInitWs; }
set { bInitWs = value; }
}
private string sMethodName;
public string MethodName
{
get { return sMethodName; }
set { sMethodName = value; }
}
private bool bCallWs;
public bool CallWs
{
get { return bCallWs; }
set { bCallWs = value; }
}
private DateTime dtDebutSession;
private DateTime dtEndSession;
private DateTime dtDebutWS;
private DateTime dtEndWS;
public void startWScall()
{
dtDebutWS = DateTime.Now;
}
public void stopWScall()
{
dtEndWS = DateTime.Now;
}
public LogFile()
{
dtDebutSession = DateTime.Now;
}
public void toFile()
{
dtEndSession = DateTime.Now;
Uri pathUri = new Uri(Path.GetDirectoryName(Assembly.GetAssembly(typeof(xxxxx)).CodeBase));
string path = pathUri.AbsolutePath + "/logs/";
path = System.Web.HttpUtility.UrlDecode(path);
System.IO.Directory.CreateDirectory(path);
string name = DateTime.Now.ToString("yyyyMMdd") + ".txt";
// create a StreamWriter and open the file
StreamWriter logFile = new StreamWriter(path + name, true, System.Text.Encoding.GetEncoding("iso-8859-1"));
logFile.Write(ToString());
logFile.Close();
}
override
public String ToString()
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("Session begin : " + dtDebutSession);
sb.AppendLine("Method : " + sMethodName);
sb.AppendLine("Init WS : " + bInitWs);
sb.AppendLine("Calling WS : " + bCallWs);
sb.AppendLine("Callins WS Duration : " + (dtEndWS - dtDebutWS).TotalSeconds);
sb.AppendLine("Duration : " + (dtEndSession - dtDebutSession).TotalSeconds);
sb.AppendLine("Session end : " + dtEndSession);
sb.AppendLine("Result : " + Enum.GetName(typeof(ErrorCodes), error.RC));
if (error.RC != ErrorCodes.OK)
{
sb.AppendLine("Exception Name : " + error.ExceptionType);
sb.AppendLine("Exception Message : " + error.ErrorMsg);
}
if (error.RC != ErrorCodes.OK || bPrintDatas == true)
{
sb.AppendLine("--------------------");
sb.AppendLine(sXmlIn);
sb.AppendLine("--------------------");
sb.AppendLine(sXmlOut);
}
sb.AppendLine("----------------------------------------");
return sb.ToString();
}
public void toXML()
{
}
}
The problem is, sometimes (I can't redo the problem), an exception appears :
Date : 11/02/2014 20:19:49
Exception :
System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]
- The process cannot access the file 'C:\xxx\xxxt\xxx\bin\logs\20140211.txt' because it is being
used by another process.
Stack Trace : Server stack trace: at
System.ServiceModel.Channels.ServiceChannel.ThrowIfFaultUnderstood(Message
reply, MessageFault fault, String action, MessageVersion version,
FaultConverter faultConverter) at
System.ServiceModel.Channels.ServiceChannel.HandleReply(ProxyOperationRuntime
operation, ProxyRpc& rpc) at
System.ServiceModel.Channels.ServiceChannel.Call(String action,
Boolean oneway, ProxyOperationRuntime operation, Object[] ins,
Object[] outs, TimeSpan timeout) at
System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage
methodCall, ProxyOperationRuntime operation) at
System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage
message) Exception rethrown at [0]: at
System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage
reqMsg, IMessage retMsg) at
System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData&
msgData, Int32 type) at xxxxxxxx at xxxxxxxx in
c:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET
Files\root\24b8742a\5648f098\App_WebReferences.b9kkgfpv.0.cs:line 811
at xxxxxxxx in xxxxxxxx\tools.cs:line 547 at xxxxxxxx() in
xxxxxxxx.cs:line 48 at xxxxxxxx.Page_Load(Object sender, EventArgs e)
in xxxxxxxx.aspx.cs:line 41 at
System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object
o, Object t, EventArgs e) at System.Web.UI.Control.LoadRecursive() at
System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
I don't understand why because WCF manage concurrency between each instance of WCF entry.
EDIT :
This is the code with the Mutex added in LogFile class
private readonly Mutex mutex = new Mutex();
[...]
mutex.WaitOne();
StreamWriter logFile = new StreamWriter(path + name, true, System.Text.Encoding.GetEncoding("iso-8859-1"));
logFile.Write(ToString());
logFile.Close();
mutex.ReleaseMutex();

Answer 1

At first you should wrap your mutex usage in a try finally block
private readonly Mutex mutex = new Mutex();
[...]
try
{
mutex.WaitOne();
StreamWriter logFile = new StreamWriter(path + name, true, System.Text.Encoding.GetEncoding("iso-8859-1"));
logFile.Write(ToString());
logFile.Close();
}
catch(Exception e)
{
// trace your exception somewhere useful here!
throw;
}
finally
{
mutex.ReleaseMutex();
}
You are also using the Mutex wrong, have a look at the very good example here:
What is a good pattern for using a Global Mutex in C#?